Closes anomalyco#19855

Summary

When pressing Escape to cancel an in-progress LLM generation in the TUI, an unhandled promise rejection stack trace bleeds through to stderr, corrupting the terminal display.

Root Cause

Three fire-and-forget async calls without .catch() handlers:

1. session.ts:384 (primary): The abort HTTP endpoint calls SessionPrompt.cancel() without await or .catch(). cancel() internally calls cb.reject(new Error("Session cancelled")) to reject pending promises. Since the endpoint returns c.json(true) before cancel() completes, the rejection is unhandled and Bun writes the stack trace to stderr.

2. prompt/index.tsx:262: sdk.client.session.abort() called without .catch() when Escape is pressed twice.

3. prompt/index.tsx:654: sdk.client.session.command() called without .catch().

Fixes

• session.ts:384: await SessionPrompt.cancel(...).catch(() => {})
• prompt/index.tsx:262: Added .catch(() => {}) to abort call
• prompt/index.tsx:654: Added .catch(() => {}) to command call

Test

Added test/session/cancel.test.ts:

• Verifies SessionPrompt.cancel() rejects pending callbacks without producing unhandled rejections
• Verifies cancel on non-existent session doesn't throw

Note: Test requires @ai-sdk dependency fix to run (pre-existing issue with createProviderToolFactoryWithOutputSchema export).

How to reproduce

1. Start a session in the TUI
2. Send a message that triggers LLM generation
3. Press Escape twice during generation
4. Observe stack trace text bleeding over the TUI rendering